structlog

A lightweight structured logging tool for Node.js without any dependencies.

Example

By default this tool will generate logs like the following:

2022-03-09T19:57:48.962Z [error] i'm an error [/structlog/foo.js:5] thread=MAIN logId=017f705b-4200-0002-1101-720541fa117c 
2022-03-09T19:57:48.963Z [warn] i'm a warning [/structlog/foo.js:6] thread=MAIN logId=017f705b-4200-0000-e4a6-f1df2ca4f248

However, you can configure both the log and timestamp formats.

Usage

To use this logging tool, all you need to do is install it:

yarn add structlog

And use it like so:

import { logger } from 'structlog'

logger.error('error!')

Importing logger will give you a ready-made instance of StructuredLogger with the default config, so you don't need to instantiate a new logger instance each time or pass down references to an instance.

However, you can configure options by instantiating StructuredLogger yourself, like so:

import { StructuredLogger } from 'structlog'

const logger = new StructuredLogger({ timestampFormat: 'unix' })

Options

You can configure the following options by passing them in an object as a parameter when creating StructuredLogger :

Option	Default value	Accepted values	Description
timestampFormat	'iso'	'iso' , 'gmt', 'unix', 'timestring' ,'localestring'	Timestamp format to use.
logFormat	'{timestamp} [{type}] {message} [{path}] {tags}'	Any string	Log format to use {} to define variables. Accepted variables: timestamp, type, message, path, tags.
pathFormat	'{filePath}:{lineNumber}'	Any string	Format to use for the path component of the log. Use {} to define variables. Accepted variables: filePath, lineNumber, functionName, methodName, typeName.
useColors	false	true, false	Whether logs should be printed with colors according to the type (e.g. error = red).
useThreadTagsExtension	false	true, false	An extension that automatically adds a thread tag to the log specifying what thread the log happened in.
useLogIdExtension	false	true, false	An extension that automatically adds a logId tag to the log, with a unique ID as its value.
pathStackDepth	0	Any number	(Advanced) Level of depth to determine the path portion of the log from. For example, if you write a wrapper over the logger, set this to 1 so that the path will reflect the code that called your wrapper, rather than the wrapper itself.